Hemolytic activity

assay L. monocytogenes strains were grown in BHI-SPC GSK3326595 medium overnight with shaking at 37°C. The following morning, each culture was diluted 1:20 into fresh medium in duplicate. These cultures were grown at 37°C with aeration to an optical density at 600 nm (OD600) of 0.5. At this point, penicillin G was added to a final concentration of 0.03 μg/ml to one of the duplicate cultures and the incubation was continued for a further 2 hours, when the cells reached early stationary phase. The number of viable bacteria present in both cultures was determined by plating serial dilutions onto BHI-SPC agar and counting the colonies after overnight incubation at 37°C. The hemolytic activity in the supernatants from both cultures was assayed by determining the level

of hemoglobin released from sheep red blood cells (SRBC), essentially as described previously [33]. Briefly, a 1 ml sample of culture was centrifuged to pellet the cells and 20 μl of the supernatant was added to 1 ml of PBS (phosphate-buffered NVP-LDE225 in vivo saline, pH 5.6) containing SRBC, and this was incubated at 37°C for 30 min. To avoid complete hemolysis, the final amount of SRBC used in the assay was 0.5%, 1% or 2%, and was individually determined for each strain. The reactions were then centrifuged to pellet unlysed cells and the hemoglobin absorbance in the supernatants was measured at 410 nm. this website Hemolytic activity was expressed as the percentage of complete

hemolysis, which was determined by lysing appropriate amounts of SRBC with 1% Triton X-100 per 109 bacteria. The presented 17-DMAG (Alvespimycin) HCl results are the average of at least three independent experiments, each carried out in triplicate. Sequence analysis Chromosomal DNA fragments inserted upstream of hly in pAT28-hly derived plasmids were sequenced with the primers seq-1and seq-2. The sequences were compared with the L. monocytogenes EGD-e genome using the BLAST program on the NCBI website. Total RNA isolation For RNA isolation, a culture was inoculated with a single colony of wild-type L. monocytogenes EGD and incubated overnight at 37°C. The following morning, the culture was diluted 1:50 into fresh medium in duplicate. These cultures were grown at 37°C with aeration to an OD600 of 0.4. At this point, penicillin G was added to a final concentration of 0.09 μg/ml to one of the duplicate cultures and incubation at 37°C was continued for an additional 30 min. Total RNA was isolated using the hot acid phenol procedure [34]. Briefly, 1 ml of the separate cultures was centrifuged (12,000 × g for 30 s) and the cell pellets were immediately resuspended in ice-cold lysis buffer (20 mM sodium acetate, 1 mM EDTA, 1% sodium dodecyl sulfate, pH 5.2). Each cell lysate was added to an equal volume of preheated (65°C) acid phenol-chloroform-isoamyl alcohol with 200 mg of glass beads and placed in a heating block (65°C) for 10 min with frequent vortexing.